In telecommunication networks, various independent networks (domains) communicate amongst themselves. Each domain can have various internal routing protocols. Passing communications from one domain to another, across domain boundaries (through border nodes), requires the advertising of a link and node topology so that a node, originating data, can determine the appropriate path (between nodes) through which the data should be passed. The links and nodes can be advertised as a network topology, which can represent a real-time view of the status and availability of intra and inter domain connections amongst nodes using various types of advertise information, such as routing information (e.g. destination address, priority level, least-cost route, minimum route delay, minimum route distance, route congestion level, bandwidth, color, metric, and the like). Data originating nodes can use the advertised information (called routing considerations) to determine the appropriate path amongst various potential paths.
Routing protocols allow networks to dynamically adjust to changing conditions. There are several conventional routing protocols, e.g. Open Shortest Path First (OSPF), Intermediate System to Intermediate System (IS—IS) and Private Network Node Interface (PNNI) routing protocols. Conventional art systems attempt to extend these for multi-domain environments within the ITU-T (ITU-T is the telecom standardization organization of the International Telecommunication Union (ITU)).
Conventional systems use a method of abstraction for illustrating the actual internal domain topology between intra-domain border nodes and may advertise all border nodes (BN) with abstract links interconnecting them. In such a system, as the number of border nodes increases, a full mesh of abstract links is advertised. When a border node is added or removed, a full set of links connecting the border node to every other border node can be affected. In this method, if there are N−1 nodes in the network and an Nth node is added, N2 links must be advertised. Thus, this system is not scalable. Further, in some circumstances, one may not want to have the actual border node intra-domain topology advertised.
Alternatively, conventional methods may advertise the domain as a single virtual node, with no internal structure. This method is simple, but has the several disadvantages. For example, interfaces need to be renumbered to be unique in the context of the single virtual node, rather than using their original interface identifiers, which are only unique in the context of the associated border node. Thus, this method is administratively more complex. Additionally, no internal restrictions or metrics can be shown for the single virtual node, since nodes are not advertised with internal properties. This means that calculation of the end-to-end metric for a connection may not be accurate since it does not take into account the cost of crossing the domain, potentially leading to inefficient routing or failure to meet end-to-end path constraints.